Microelectromechanical systems (MEMS) are the integration of mechanical elements, sensors, actuators, and electronics on a substrate through micro fabrication technology. These devices, known as ‘micro-machines’ are manufactured using micro fabrication techniques. If microelectronic integrated circuits can be thought of as the “brains” of a system, then MEMS can be considered to be equivalent to the “eyes” and “arms”, and together they create a complete microsystem to sense and control the environment. Sensors gather information from the environment through measuring mechanical, thermal, biological, chemical, optical, and magnetic phenomena. There are many MEMS devices, including accelerometers, gyroscopes, temperature sensors, chemical sensors, micro-lenses, comb drive actuators, piezoelectric actuators, blood analysis chips, genetic analysis chips, adaptive optics, arrayed fiber optic switch chips, automotive engine analysis sensor suites, and micro satellite components. Some of these devices were first realized as non-MEMS devices using traditional fabrication techniques many decades ago. The integrated circuits then process the information derived from the MEMS sensors and through some decision making capability direct the actuators to respond by moving, positioning, regulating, pumping, and filtering, thereby controlling the environment for some desired outcome or purpose. Because MEMS devices are manufactured using batch fabrication techniques similar to those used for integrated circuits, unprecedented levels of functionality, reliability, and sophistication can be placed on a small silicon chip at a relatively low cost.
Concerning the size definitions of these “small” devices, three categories are often used: meso, micro, and nano. Meso is a prefix meaning mid, medial, intermediate, or middle. Meso sized devices typically have feature sizes between 2 mm and 50 mm. Micro sized devices have feature sizes between 500 nm and 2 mm. Nano sized devices have feature sizes between 1 nm and 500 nm. Generically speaking, the term ‘MEMS’ is often used to describe devices with all three feature sizes. Traditionally, most MEMS devices have been realized in silicon based technology, largely borrowed from microelectronics technology. However, in recent years a variety of other materials have been used to create MEMS devices, including polymers, ceramic, gallium arsenide, silicon carbide, and plated metals. The micromechanical components are traditionally fabricated using compatible “micromachining” processes (typically based on chemical etching or machining) that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices. MEMS is an enabling technology allowing the development of smart products, augmenting the computational ability of microelectronics with the perception and control capabilities of microsensors and microactuators and expanding the space of possible designs and applications.
MEMS devices need to be packaged to protect them from environmental contamination and damage, and this is usually the most expensive and critical part of the silicon MEMS fabrication. In the field of meso-MEMS devices, packaging is equally important and costly. It would be a great addition to meso-MEMS technology if a cost effective package could be created.